Gaskets are often used to provide a fluid type seal between two engaging, confronting or mating parts. A common example includes pipes or similar conduit having machined flanges which are butted together about a gasket, the gasket having a large central opening matching that of the interior of the pipes as well as much smaller peripheral holes registering with like holes in the flanges generally to receive bolts or the like, to secure the assembly together. Gaskets are used for many other like applications, such as for cylinder heads of internal combustion engines, in valves, and the like.
In general, gaskets comprise a base sheet of uniformed thickness which may be sheet metal or of fibrous composition held together by a suitable bonding agent, and a deformable coat or bead which may cover all or only selected areas of the sheet. In use the coat or bead deforms or spreads under pressure of forcing together the parts between which the gasket material lies and aids in realizing the desired fluid-type seal between the parts.
The ability of a gasket to perform its function depends in large part on the ability of the sealant to form a fluid-type seal. In the past, reliance has been almost exclusively on a solid coat or layer of a sealant which permanently deforms or flows under pressure to effect the seal.